In modern recreational vehicles such as mobile homes, caravans and pleasure crafts there is a tendency to provide the living area of the vehicle with modern household appliances. It has shown desirable that these modern appliances differ as little as possible from corresponding appliances normally used in permanent homes. For example refrigerators used in modern recreational vehicles are very similar to household refrigerators what concerns the dimensions, number and type of compartments and capacity. A modern refrigerator for a recreational vehicle may thus comprises at least one refrigerator compartment and at least one freezer compartment and may have outer dimensions (H×W×D) up to 165×81×61 cm (65×32×24 inches).
A suitable choice of refrigerator for mobile use, for example in recreation vehicles, is an absorption refrigerator. Such an absorption refrigerator may comprise a single refrigerator compartment or fresh food compartment, maintaining the temperature at approx. 5° C. Normally, however, it comprises one freezer compartment maintaining the temperature at approximately −18° C. and one refrigerator compartment maintaining the temperature at approximately +5° C.
Briefly, the absorption refrigerator comprises a cabinet and an absorption refrigerating system including a heater or boiler, a water separator, a condenser, an evaporator and an absorber. These components of the refrigerator system are arranged in series in a closed loop with respect to a refrigerator medium, usually a water-ammonia mixture, which flows within the refrigerating system.
The evaporator, which forms a cold part of the refrigerator system, is normally arranged inside the compartments to be cooled. It may comprise a first tube section arranged to take up heat from the freezer compartment and a second tube section arranged to take up heat from the fresh food compartment, thereby lowering the temperature within the compartments.
The boiler, water separator, condenser and absorber together form a hot part of the refrigerator system and are normally arranged on the outside of the rear wall of the cabinet. Since these components generate heat, they need to be insulated from the compartments. This is done by arranging an insulation material, such as fibreglass or polystyrene foam, in the rear cabinet wall. Such insulation material is normally arranged also in the other cabinet walls and the cabinet doors for reducing heat transfer from the ambient atmosphere into the compartments.
The water separator, condenser and absorber need to be cooled. Such cooling is normally effected by allowing ambient air to pass over these components of the refrigerator system. The heat leakage from the boiler on the other hand should be kept as low as possible, for achieving satisfactory efficiency.
At recreational vehicles, such as mobile homes and caravans, the refrigerator is normally placed in a specially designed recess or niche arranged in the living area of the vehicle. The niche is arranged in proximity to an outer wall of the vehicle and comprises niche walls that extend inwardly from the inside of the vehicle's outer wall. The niche walls are further arranged to sealingly contact the top, side and possibly bottom walls of the refrigerator cabinet, such that the rear portion of the refrigerator is enclosed in the niche. The space defined by the inside of the vehicle's outer wall, the niche walls and the rear wall of the refrigerator cabinet is normally referred to as the cooling unit recess or the CUR. At installation of traditional refrigerators the hot part of the refrigerating system or the cooling unit is located within the CUR. By this means heat generated by the refrigerator system is prevented from dissipating into the living area of the vehicle. For cooling the refrigerator system, a lower and an upper ventilation aperture is arranged through the outer wall of the vehicle, such that the CUR is in communication with the atmosphere outside of the vehicle. Hereby, ambient air is allowed to enter through the lower aperture, and to exit through the upper aperture. Heat generated by the refrigerator system is transferred to the air, whereby a self-circulating airflow is created, which cools the refrigerator system.
Such an arrangement entails certain disadvantages. The construction and mounting of the niche per se require structural elements and labour and thereby entails costs. In order to achieve a great enough airflow through the CUR, the cross sectional area with respect to the airflow direction needs to have a certain smallest dimension. Normally this means that the volume of the CUR becomes at least approx. ¼ of the total inside volume of the storage compartments. The rate between useful food storage volume and total volume occupied by the refrigerator and CUR is limited thereby. The apertures of the CUR further need to be of a certain smallest dimension, which means that comparatively large openings need to be cut out in the vehicle wall. The apertures further need to be covered by correspondingly large grids or nets for preventing dust, insects and the like to enter the CUR. For satisfactory functioning of the known arrangement it is also required that the lower aperture is arranged at or below the lower end of the refrigerator whereas the upper aperture needs to be arranged at or above the upper end of the refrigerator. This means that the apertures need to be positioned differently for every different height of refrigerator to be installed and used in the vehicle. Especially if the refrigerator is to be placed beneath a bench in the vehicle, it is normally not possible to arrange the upper aperture high enough, whereby the cooling and efficiency of the refrigerator system is adversely affected. The necessity of arranging a pre-installed niche in the vehicle, especially since it needs to be arranged at an outer wall, also limits the free choice of where to place the refrigerator.
A further problem related to the prior known arrangements occurs at use under winter and other cold ambient conditions. At start up of the refrigerator at such cold conditions, it might happen that the refrigerator media has frozen. Not until heat generated by the boiler has melted the media, the refrigerator may operate properly. In order to speed up such melting, the airflow through the CUR may be reduced or prevented. In order to achieve this, specially designed winter condition covers need to be applied to the grids covering at least one of the openings in the outer walls of the vehicle. The necessity of such winter condition covers naturally adds to the costs and renders handling of the refrigerator more complicated.